Induction heating apparatus



Jan. 17, 1950 wrF. WELLS 2,495,193

INDUCTION HEATING APPARATUS Filed June 15, 1946 WITNESSES: I INVENTOR ,A-M. flfflmfih/. BY 72W (1 %A a. my

ATTORNEY Patented Jan. 17, 1950 UNITED s TAT ES PATENT orFics INDUCTION HEATING APPARATUS? William F. Wells, Baltimore,.. Md., assignor to Westinghouse Electric Corporation, East Pitts burgh,- PaL, a corporation of Pennsylvania Application June 15, 1946, Serial'No. 6'76-,9;l2-

3 Claims.

While my invention .has broader aspects, ,it described .herein with special emphasis onan induction heating apparatus for heat treating helical or coil'springs having one or both end turns contacting the next adjacent turn so thatthe spring has, in effect, .an electrically. short-circulated. turn.

When itlis attempted'to inductively heat such coilsprings inthe customary manner, that is, with magnetic field lines parallel'to the axis of the spring, overheating is encountered in the turn which is shorted on itself or contacts an inner turn. By heating such a spring inductively with magnetic field lines passing through the spring substantially perpendicularly to its axis, in accordance with my invention, there is no electric current flow around the short-circuited turn.

The spring is uniformly heated without localized I overheating, especiallywhen the spring is also rotated'about its axis so that all of its sections are subjected to the different parts of the heat-producing alternating magnetic field.

My invention has for another objective the heat-treatment of round metal objects or workpieces within an induction-heating coil shaped to a contour of the work-pieces. Thus, for example, ior an elongated'helical spring having turns of substantially the same diameter, I provide an induction-heating coilof rectangular shape. which is elongated in the'length-direction of the spring.

Other objects, features and innovations of my invention will be apparent or'discernible. from the followingdescription of the preferredembodiment, which description is to be taken in conjunction with the accompanying" drawing, in which:

Figure l'is-a schematic perspective viewof an application of my invention for heating'helical springs, with a quenching means omitted for clarity;

Fig. 2 is a sectional View substantially on the line IIII'of'Fig. l-with-a quenching means added; and

Fig; 3 is aschematicwiring diagram showing the principal parts of a second system utilizable with the apparatus of Figs. 1 and 2.

A specific'work-piece that can be heated in the apparatus sh'own in Figs 1 and Z constitutes a helical spring 2 of a steel that can be hardened. The spring 2 has end turns 4 terminating in tip-ends 6 which press against, or otherwise contact, the adjacent metal of the next turn of the spring so that, electrically speaking, a complete path is provided for current-flow around each end-turn ofthe spring.

The spring 2 is heated when an inductionheating coil, indicated in its entirety by the reference numeral 8, is energized by an alternatingcurrent source of suitable frequency. The coil 2. 8 comprises a number. of rectangular turns-of hollow copper tubing. that'canbe water cooled.

The spring 2 is supported on I a pair: of horizontally-directed rotatable rods or rollers 9 and Ill-of a suitable heat-resistant materiala Anonmetallic refractory, such as-silicon-carbide; is

satisfactory. The rollers -9- and l0-arerotatablysupported in a frame which is indicated in its entiretyv by the reference numeralv 12; the frame comprising a stationary member I4 in which the I roller 9 is rotatably supported; and a second.

member lS in which the roller H1 is rotatably sup; ported. Theirame-member I6 is-s1idable I for purposes to be laterdescribed.- Ends of the rollers 9 and!!! extend beyond the frame-membersi l' and 'l B, and. have sheaves. l 8 adaptedto be rotated by a driving wheel 26% with whichithe mesh- The" when in normal work-receiving position. driving wheel EQiS driven, throughgearing-ZZ; by-

a motor-driven shaft 24 which also'drives; through 1 the. gearing, atimer shaft 26 having a cam 28 bearing-against a roller 35 'rotatably-securedto the slidable frame-member IS;

The frame-member i6 is provided with rods 32Twhich= are slidably received in holes or jourrials in thestationary member I 4; and with a rod-- 31 slidably received.v in a hole in a'stationary post 36 which maybe part ofthe stationary frame-memb'eri i, if desired, Anchored tospaced stationary lugs 38, on opposite lateral sides'of' thepost 36, are a pairof tension=springs40= whichtends to pull the slidable frame-member l6- away from the stationary frame-member l4 and toward the post 35 which therefore: also servesas a stop.-

Duringi rotation of the time shaft-26; a cir-- cularcam-surface 42; on the cam 28, engages the roller: 36" and keeps the frame-member" 16* in: the position shownwhile the driving wheel ZU-rOtates-the rollers 9 and E0. The rollers cause the spring 2 to rotate aboutits own axis which.

is parallel to a long side of'the rectangular induction-heating coil 8. If the coilt is'energized the spring will be heated while'it is being'rotated.

When the 'cam has been. rotated to a point where its indent'surface ill'reaches the roller 30, the tensionlsprin'gs Gilyank the frame-member [6' toward the post 36; pulling the'roller Sil -along with it, sothat the heated spring 2 drops between the rollers 9 and lil "into a quench tank 45 1mmediately below the rollers.

A control may be provided for timing the heat ing of the spring or work-piece 2. To this end a switch 46 is provided which is normally-biased to open position but forcedinto closed "position by the slidableframe-member IS in its work receiving position shown in Fig. 1. When the springs 40 move the slidable frame-member IS, the switch 46 opens automatically.

Referring to Fig. 3, the switch 46 controls a relay 48 in a circuit 50; the relay being of a type having an armature or core 52 which it cannot, upon energization, raise from a back or released position, but which it can maintain in front or holding position if the core 52 is otherwise moved to this front position. A handle 54 is shown attached to the bottom of the core 52, by which the core can be manually raised into the front position where it will be held if the relay 48 is energized.

The core 52 operates a plurality of movable contacts 56 and 58. The movable contact 56, in front position, is instrumental in completing a circuit 60 to a motor 62 which drives the shaft 24. The movable contact 58, in front position, is instrumental in completing a circuit 64 to a relay 66 which, in energized condition, completes a circuit 68 for energizing the induction-heating coil 8.

In operation, while the core 52 of the relay 48 is in its back position and the frame-member I6 is in its work-receiving position, so that the switch 46 is closed, a spring 2 may be placed upon the rollers 9 and I9. The core 52 may then be pushed into its front position where it will be automatically held because the circuit 50 is complete. In front position of the core, the contact 56 energizes the motor 62 which rotates its shaft 24 and hence the drive wheel 20 and the spring 2. At the same time, the contact 58 causes application of heating power to the induction-heating coil 8 so that the spring 2 is heated by magnetic flux passing axially through the coil 8, that is, perpendicularly to the axis of the spring 2. At the same time, the shaft 24 of the motor 62 drives the cam 28 so that its surface 42 moves past the roller 36 until the indent surface 44 of the cam reaches the roller 30. The springs 49 can then pull the slidable frame-member I6 toward the post 36, separating the rollers 9 and H1. The heated spring 2 is consequently released and drops into the liquid in the quench tank 45. As the frame-member I6 is withdrawn, the switch 46 opens and deenergizes the relay 48 which drops its core 52, moving the contacts 56 and 56 to open or back position. Opening of the circuits 62 and 64 by these contacts deenergizes the motor 62 and disconnects the power supply from the coil 8.

For restoring the apparatus to heat-treating condition, a separate manually-operable switch '10 can be temporarily operated to energize the motor 62 and restore the cam 28 to a position where it forces the frame-member I6 into workreceiving position; or the cam driving means may be manually turned.

Obviously the speed of rotation of the rollers 9 and I0, and hence the spring 2, will be determined by the diameter of the driving wheel 2!] and by the gearing reduction in the gear box 22; and similarly the timing of the heating of the spring 2 will be controlled by the gearing in the box 22 between the driving shaft 24 and the cam shaft 26, and by the peripheral length of the outer surface 42 of the cam 28.

It is to be observed from Figs. 1 and 2 that the inside of the rectangular multi-turn inductionheating coil 8 provides a work-receiving space of sufficient size and depth to encompass substantially the entire spring 2. The rollers 9 and ill lie under this Work-receiving space of the coil 8 and support the spring 2 so that the short-circuited end turns 4 of the spring face the shorter opposed turn-sides of the coil 8 and the axis of the spring is parallel to the longer opposed turnsides of the coil 8. The rollers 9 and I6 must provide a cylindrical spring-supporting surface which is axially sufficiently elongated to let the spring 2 roll on the surface without a turn of the spring catching on an end of the rollers.

While I have described my invention in its preferred form, it is evident that its teachings are generally applicable to any suitable elongated round Work-piece capable of being rotated about a central axis extending in the direction of its length. It is also evident that equivalent parts may be substituted and modifications can be made in the apparatus herein disclosed to accommodate such and other work-pieces for heat-treatment in accordance with the general teachings of my invention.

I claim as my invention:

1. Induction heating apparatus suitable for heating a helical spring having shorted end-turns, comprising a helical induction heating coil generally rectangular in a substantially horizontal cross-sectional plane, said coil having an upstanding axis and comprising substantially straight opposite turn-sides, a pair of elongated substantially straight horizontal rollers under said coil substantially parallel to a pair of said opposite turn-sides, said rollers being continuous in length for a major part of the length of each of the last said turn-sides and adapted to support a helical spring with its axis parallel to said turn-sides.

2. A helical induction heating coil generally rectangular in a substantially horizontal crosssectional plane, said coil having an upstanding axis and comprising a plurality of turns, the coilturns having substantially straight opposite turnsides, means to rotatably support a workpiece entirely Within said coil for rotation inside of said coil about a horizontal axis, said means comprising pair of adjacent work-supporting and rotating substantially horizontal rollers under said coil, parallel to a pair of said turn-sides.

3. An invention including that of claim 2 but further characterized by timer means for periodically spreading said rollers, whereby to allow work on said rollers to drop.

WILLIAM F. WELLS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,052,010 Bailey Aug. 25, 1936 2,308,240 Goodridge Jan. 12, 1943 2,324,525 Mittelmann July 20, 1943 2,371,459 Mittelrnann Mar. 13, 1945 2,417,678 Cox Mar. 18, 1947 2,419,619 Wood Apr. 29, 1947 OTHER REFERENCES Thermonic catalogue, page 29 of Induction Heating Corporation, published 1943.

American Machinist, Oct. 12, 1944, pages 101404.

Steel, July 9, 1945, pages 104 and 162.

Electronic Industries, January 1946, page 84. 

